Alzheimer's disease is the most common cause of dementia, and is characterized by the loss of intellectual and social abilities severe enough to interfere with daily functioning. In Alzheimer's disease, healthy brain tissue degenerates, causing a steady decline in memory and mental abilities. Alzheimer's disease is not a part of normal aging, but the risk of the disorder increases with age. About 5 percent of people between the ages of 65 and 74 have Alzheimer's disease, while nearly half the people over the age of 85 have Alzheimer's.
Two types of neuron pathology, plaques and tangles, are common in patients with Alzheimer's disease. Extracellular plaques are clumps of a normally harmless protein called beta-amyloid (Aβ) which may interfere with communication between brain cells. Tangles are the internal support structure for brain cells depends on the normal functioning of a protein called tau. In people affected with Alzheimer's disease, threads of tau protein undergo alterations that cause them to become twisted. Many researchers believe this may seriously damage neurons, causing them to die and leading to memory deficit.